A closed container with impermeable diathermal walls contains some amount of gas. If the gas is considered to be a system, what type of system will it be?

Explanation

As the walls of the container are impermeable, flor of matter into or out of the system is not possible. Again, the walls are diathermal. Thus, the exchange of heat between the gas and the surroundings is possible. Hence, the gas is a closed system.